Process for the reduction of metalliferous materials by magnesium



March 15, 1938. G. N. KIRSEBOM -2,111,367

MPROCESS FOR THE REDUCTION OF METALLIFEROUS MATERIALS BY MAGNESIUM Filed Oct. 12, 1935 IN l/E/V T K GuTAF A/EWTON $835807 3, 41M, w%m

Patented Mar. 15, 1 938 UNITED STATES PATENT OFFICE PROCESS FOR THE REDUCTION lVIETAL- LIFEROUS MATERIALS BY MAGNESIUM Application October 12 1935, Serial No. 44,683 In Great Britain October 23, 1934 1 Claim.

This invention relates to the reduction 01 metalliferous materials using magnesium as reducing agent, and is applicable to the treatment of such metalliferous materials as contain metals the oxides of which have a heat of formation less than that of MgO.

Improved methods of producing magnesium metal have made it possible to use the latter economically as a reducing agent in the preparation w of certain metals from difficultly reducible compounds, in particular, refractory oxides. Magnesium and alloys of magnesium react, however, very easily with both the oxygen and nitrogen of the atmosphere at elevated temperatures.

15 Moreover, the reduction reaction is strongly exothermic, and if magnesium powder, for example, is mixed with an oxide, and the mixture is ignited in the manner of the alumino-thermic process, the reaction takes place with almost explosive violence.

I have now found that if metallic magnesium be heated together with, for example, another alkaline earth oxide, such as barium oxide, in a closed vessel provided with, for example, a tube closed with an oil seal, the reaction takes place sufficiently quietly to avoid too high a pressure in the reaction vessel. Moreover, carrying the reaction out in a closed vessel prevents the interfering action of the oxygen and nitrogen of the atmosphere, the small quantity of air in the vessel bemg used up in the early stages of the heating by the action of a small quantity of the magnesium.

On the other hand, the closed vessel may be evacuated by means of a pump at the beginning of the reaction in which case an oil seal is not necessary.

Accordingly the present invention is for a process for reducing metalliferous materials and recovering metal values therefrom, which comprises heating the said metalliferous material together with metallic magnesium in a closed vessel to a temperature above the melting point of magnesium.

An improved reaction, and consequently better results, are obtained if the metalliferous material to be treated is in other than powder form, i. e. in lumps or pieces of suflicient size to slow down the reaction enough to prevent any considerable rise in temperature in the reaction vessel above that required to maintain the magnesium in the molten state. I

The invention is, in particular, applicable to .the preparation of alkaline earth metals other than magnesium, or alloys thereof with magnesium.

The accompanying drawing shows in longitu;

dinal section a simple form of apparatus suitable for carrying out the process of the invention. in is an iron cylinder provided with flanges ii and covers l2 and I3, fixed by bolts M to the two flanges. The cylinder is provided at I5 with an outlet connected with a pipe I6 which is bent downwardly and may be dipped below the surface of oil in a bath-l1 in order to form a pressure safety device.

The bottom end of the cylinder I0 is first closed by fixing the cover l3 and the requisite amount of magnesium introduced at the top end along with pieces of oxide of barium, strontium or calcium. The top is then closed by fixing the cover l2 and the end of the safety tubes sealed by dipping below the surface of a bath of oil ll. At the end of the run a limited amount of air may be admitted into the cylinder through a pipe [6 to prevent the oil sucking back when cooling.

Barium and strontium having a specific gravity of 3.5 will after reaction sink down to the bottom of the pot, while the dross consisting of magnesium oxide will float on top. By cooling the cylinder and removing both lids it is therefore possible to obtain cylindrical pieces of pure barium and pure strontium or alloys of these metals with magnesium, according to the relative proportions of magnesium and alkaline earth compound added at the outset. The. metal or 'alloy may be readily removed from the overlying dross. In the case of calcium, this metal having a specific gravity of 1.5 will float on top of the dross and may be likewise recovered.

The dross obtained will consist of magnesium oxide which may be mixed with magnesium and/or metal or oxide of the other three metals, according to therelative proportion of the reacting materials initially employed. This dross may conveniently be placed in an aluminium bath where the magnesium oxide is again reduced to magnesium which can again be recovered by distillation asdescribed in my prior application for Letters Patent, Serial No. 40,441, filed September 13, 1935,

The excess magnesium not reacting may be distilled over and recovered.

If,instead of an alkaline earth oxide such as baryta, a silicate is employed as starting material, an alkaline 'earth-silicon-magnesium alloy is produced.

In the specification of my prior Patent No. 1,935,245 a process is described in which, inter alia, alkaline earth metal silicates in lumps or pieces are added to a bath of molten aluminium,

whereby an aluminium-silicon alloy is produced leaving the metal 01' the silicate in the form of oxide together with aluminium oxide, the mixed oxides thus forming a dross.- The present invention provides a convenient means 01 treating this oxide dross. Thus for example beryl], which is a beryllium aluminium silicate, may be added to a bath of molten aluminium in the manner described in patent specification No. 1,935,245 whereby an aluminium-silicon alloy is produced together with a dress consisting of beryllium oxide and aluminium oxide, with metallic aluminium interspersed. This dross is in the form of small pieces, and when introduced into a bath of molten magnesium or a bath of magnesium alloy with barium, strontium or calcium, the contained beryllium oxide therein is reduced to metallic beryllium and alloys with the magnesium. I have in this way produced an alloy containing 3.6% of aluminium, 0.9% of beryllium, the remainder being magnesium.

In order to obtain a beryllium free from aluminium, the dross may be submitted to an oxidizing roast, at a temperature of 800-1000 C. prior to treatment with the magnesium. After this treatment, the dross consists practically entirely of beryllium oxide and aluminium oxide, and when treated with molten magnesium the beryllium oxide alone is reduced, and a magnesium-beryllium alloy is produced from which the magnesium can be distilled, leaving a residue of metallic beryllium uncontaminated with aluminium.

As already stated, the process of the invention may be applied to the treatment of metalliferous material in which the metal values to be recovered are those yielding oxides with heats of formation less than that of MgO. For example, tin chromium, vanadium, uranium, nickel, and the rare earth metals.

What I claim is:-

A process for preparing metallic barium which comprises heating baryta in pieces of suflicient size to prevent a rapid reaction taking place, together with metallic magnesium in a 'closed vessel without the employment of a vacuum or fluxing materials to a temperature above the melting point of the metallic magnesium.

GUSTAF NEWTON KIRSEBOM. 

